The object of this proposal is to locate and then characterize DNA sequences associated with Alzheimer's Disease (AD) or Pick's Disease (PD) or both. Six families, five at high risk for AD and one for PD, have been followed by us for ten to twelve years as part of a clinical genetic study of dementing illness. They will be the basis for this study. An additional four high risk families, less well known to us, will be further investigated and included in this study if they are willing and suitable. We propose to establish lymphoblastic cell lines on all living relatives. We will then search for linkage between DNA fragments and known markers first on chomosome 21 but then at other locations depending on our progress and developments in the related sciences.